1. Field of Invention
The present invention relates generally to pre-fabricated concrete slabs or other forms that can be rapidly connected and used for repairs on highway pavements, roadways and parking lots, bridge decks, aircraft runways, taxiways, buildings, floors, roofs, or any structure made using precast concrete forms. More specifically, the present invention is directed to an interlocking system that allows the precast slabs or forms to be quickly and easily set tightly joined together, while maintaining continuous tension reinforcement in two dimensions and with a minimum of grouting and alignment.
2. Discussion of the Related Art
Concrete structures are known to wear, deteriorate, settle and crack over time with continuous use as well as due to exposure to traffic, weather and extremes of temperature. A good example of this type of structure is a concrete roadway. One of the faster methods of repairing concrete roadways is through the use of precast concrete slabs. The damaged area of pavement is excavated and cleared and the subgrade is prepared. The concrete slabs are then positioned over the damaged area and dropped into place. It is well known that such concrete slabs can be created so that they are interconnectable. Examples of such art can be found in U.S. Pat. Nos. 1,991,931, 4,362,426, 5,626,289, 5,682,635, 6,607,329 and U.S. Patent application Serial. No. 2002/0170259.
One of the problems with the prior art concrete slabs is the inability of the slabs to provide for tension in two dimensions. For example, in the Kling et al. patent (U.S. Pat. No. 1,991,931) the slabs have interlocking tabs but they do not provide for continuous tensile forces between the precast panels, nor do they provide sufficient shear resistance between panels. The Ruckstuhl patent (U.S. Pat. No. 4,362,426), on the other hand, does appear to provide tension in two dimensions. However, the Ruckstuhl structure lacks simplicity. The connection hardware consists of a plate and screws which are inset into the precast slab, and the system uses highly precisioned complex metal parts that allow little tolerance and are impractical in the field.
A similar problem is found with the structure of the Tolliver et al. patent (U.S. Pat. No. 5,682,635). The nature of the Tolliver connection requires perfect precision, as the screw threads in the form will not be executable unless the positioning and alignment of the male and female parts are exactly true. This must be the case for every single connecting bolt, and in concrete construction in the field, this is practically impossible. Even if a user were to manage to line up one bolt and execute the connection, the next connection must also be lined up perfectly in order that the screw threads can be threaded. From a practical use standpoint, this is not ordinarily possible on a real road situation, certainly not one that seeks repair in a matter of hours. The structure of the Smith patent (U.S. Pat. No. 6,607,327) does evidence some tensile strength in two dimensions, however, it is relatively weak and does not realize the benefit of using continuous tensile steel to anchor the connectors in two dimensions.
As such, there is a need in the industry for precast concrete slabs which may be laid down so that traffic can resume in the damaged area in a matter or hours. The slabs must be strong, have satisfactory strength in two dimensions and be able to be leveled and grouted with cement mortar.
Furthermore, there is also a need in the industry to be able to construct buildings and other structures using precast connecting forms that allow for full tension in two dimensions between connecting concrete parts providing tension in two dimensions and with the added strength of steel reinforcing bars throughout the length of the form, and with a minimal amount of grouting and alignment.